Coleman-Weinberg SO(10) GUT Theories as Inflationary Models

The flat-space limit of the one-loop effective potential for SO(10) GUT theories in spatially flat Friedmann-Robertson-Walker cosmologies is applied to study the dynamics of the early universe. The numerical integration of the corresponding field equations shows that, for such grand unified theories, a sufficiently long inflationary stage is achieved for suitable choices of the initial conditions. However, a severe fine tuning of these initial conditions is necessary to obtain a large $e$-fold number. In the direction with residual symmetry $SU(4{)}_{PS}\otimes SU(2{)}_L\otimes SU(2{)}_R$, one eventually finds parametric resonance for suitable choices of the free parameters of the classical potential. This phenomenon leads in turn to the end of inflation.